MATLAB: How to define log function for arguments of type int16

image processingint16natural logsignal intensity

I am doing image processing and at some point in my code I need to find the natural log of a ratio (ration between the pre-contrast "Spre" and post-contrast signal intensities "Spost").But they are of type int16 and matlab gives me an error that "Undefined function 'log' for input arguments of type 'int16'". Could you please help me out with a solution, thanks alot.
 R2 = 1./SE;
 TE = 120; % echo time 120 ms
 SE = analyze75read('10_ep2d_ge_se_128_DCE_slice8.hdr');
 [xsize_se, ysize_se, tsize_se] = size(SE);
 for x = 1:xsize_se 
    for y = 1:ysize_se 
       IM_signal_SE = squeeze(SE(x,y,:));
       IM_signal_SE_baseline = squeeze(SE(x,y,4:15));
       Spre = mean(IM_signal_SE_baseline); % pre contrast (AVERAGE baseline signal intensity)
       Spost = IM_signal_SE - Spre; % post contrast signal SE
       *deltaR2 = 1/TE (log(Spre./Spost));*
    end
end

Best Answer

Turn them into double. E.g.,
log(double(Spre)./double(Spost))
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